1. Field of the Invention
The present invention relates to a seat track structure for adjusting a vehicle seat in a fore-and-aft direction and locking the seat in a selected position, and more particularly to a walk-in mechanism associated with a seat track structure for a front seat in a wheeled vehicle of the two door type.
2. Description of the Prior Art
A conventional seat track structure for a front seat in a wheeled vehicle of the two door type is associated with a walk-in mechanism for permitting forward movement of the front seat when a back rest of the seat is tilted forwardly and for permitting backward movement of the front seat when the back rest is raised backwardly to a selected reclining position. In general, the conventional seat track structure comprises an elongated lower stationary track secured on the floor of the vehicle compartment, an elongated upper movable track slidably mounted on the stationary track and secured to a seat cushion of the front seat, and a locking mechanism assembled with the movable track for locking the movable track on the stationary track in a selected position. The locking mechanism includes an elogated lock plate secured to the stationary track and being formed with a plurality of longitudinally equi-spaced locking holes, a crank handle having a shaft portion arranged along the seat track structure and rotatably supported on the movable track, a detent lever secured to the shaft portion of the handle for rotation therewith and arranged to be selectively engaged with the locking holes of the lock plate, and resilient means for biasing the detent lever toward the lock plate. In combination with the locking mechanism, the walk-in mechanism includes a release lever rotatably supported on the shaft portion of the handle for disengaging the detent lever from the lock plate by engagement therewith, and a linkage connecting the release lever to the back rest of the front seat in such a manner that the release lever is engaged with the detent lever when the back rest is tilted forwardly.
As is disclosed in Early Publication for Japanese Utility Model No. 55-127628, the seat track structure is further provided with a position memory mechanism which is arranged to lock the upper movable track in a predetermined position when it is moved backward. The position memory mechanism includes a memory plate in the form of an elongated resilient plate which is secured at one side thereof to the bottom surface of the lock plate to be flexible in a vertical direction at another side thereof. The memory plate extends forwardly from an intermediate portion of the lock plate and is arranged to receive the release lever thereon. When the release lever is rotated to disengage the detent lever from the lock plate, the memory plate is flexed downwards by engagement with the lower end of the release lever such that the release lever is slidably supported by engagement with the other side of the memory plate to maintain the detent lever in its disengaged position. Thus, the upper movable track can be moved forwardly or backwardly with the release lever in slidable engagement with the memory plate. When the release lever is disengaged from the rear end of the memory plate during backward movement of the movable track, the detent lever is returned to engage the lock plate thereby to lock the movable track on the stationary track in the predetermined position. In such an arrangement of the conventional position memory mechanism, a leg space for the passenger on the rear seat is narrowed due to presence of the memory plate, and slidable engagement of the release lever with the memory plate may not be maintained in a stable condition.